The present invention relates generally to an audio playback apparatus and method for an audio system, and more particularly, to an audio playback apparatus and method for outputting sounds containing a sound field in order to better appreciate performances.
A sound field is an indication of audio peculiarities which are generated in accordance with the environment of a given location, such as a concert hall, excluding the sounds actually played therein, such as a performance. A sound field is made up of a direct wave reaching a listener's ear directly from the point of sound origin (e.g., a stage), and a group of reflection waves reflected by the walls, ceiling and floor (as well as other permanently fixed obstacles) and thereby reaching the listener's ear at a time determined according to the distance from the sound source. Further, the reflection wave group is divided into two subgroups: one sub-group of waves which is first reflected by the left and right walls, and the other which is repeatedly reflected and re-reflected after the first reflection to thereby reach the listener's ear from all directions and in an irregular pattern.
Along with efforts to reproduce the original sound of a high-quality sound source, significant improvement has been achieved with respect to frequency characteristics or dynamic range, with the advent of digital audio players such as a compact disk player or digital audio tape player. However, an audio playback technique for reproducing the sound produced in a concert hall or studio like the original sound in a listening room is unsatisfactory at present, in view of the space and time dimensions of the original sound.
In a recently developed audio/video system, since a transmission technique for audio and video signals is unsatisfactory for transmitting a sufficient amount of information, and particularly, since images are planar, the spatial audio playback technique is more of a necessity in the reproduction of sound with a feeling of presence.
In FIG. 1, a conventional audio playback apparatus comprises a Dolby pro-logic decoder 11 and a sound field processor 12, and outputs audio signals L, R, C, FL, FR, RL and RR for seven channels.
An audio signal digitized in an audio signal processor (not shown) of an audio system is input to Dolby pro-logic decoder 11. Dolby pro-logic decoder 11 separates and outputs the input audio signal into four signals: a left signal L, a right signal R, a center signal C, and a surround signal S.
The left signal L, right signal R, center signal C, and surround signal S are input to sound field processor 12, which converts and outputs them into four sound field signals: a front left signal FL, a front right signal FR, a rear left signal RL, and a rear right signal RR.
In the conventional technology, the audio signal is reproduced via two channels for left and right signals, or reproduced via seven channels for the left signal, right signal and center signal L, R and C which are the output signals of Dolby pro-logic decoder 11, and the front left signal FL, front right signal FR, rear left signal RL and rear right signal RR which are the output signals of sound field processor 12, while containing a sound field.
With a conventional audio system in which audio signals are output through two channels for left and right signals, a listener cannot feel a "presence" quality of the sound. For a feeling of presence, a sound-field signal and a Dolby pro-logic signal are coupled to output audio signals for seven channels. For the listening environment of an ordinary home environment, however, it is not easy to install rear speakers, and moreover, a power amplifier and speakers for rear outputs are also required.